The need for developing effective treatment modalities for the injured and failing heart is expanding, as cardiac disease continues to take more human lives than all cancer combined. Cardiac muscle generated from human induced pluripotent stem cells (iPSCs) could serve as a model for studies of heart injury and regeneration, if the tissue would be mature enough to acquire adult-like phenotype. The lack of maturity and patient specificity are limiting the utility of currently available models. Three advances, achieved in our labs during our previous grant cycle and recent preliminary studies, form basis for the proposed new approach to studies of cardiac injury and regeneration: (a) Adult-like human cardiac muscle grown from human iPSCs (Ronaldson-Bouchard et al, Nature); (b) Perfusable network of channels serving as a template for vascularized tissues (Zhang et al, Nature Materials 2016) and (c) Heart regeneration in an animal model using human iPS-CM derived exosomes (Liu et al, Nature Biomedical Engineering, 2018). We propose to build upon these advances and bioengineer patient-specific vascularized human heart muscle using iPSCs from diverse populations, and study the individual differences under normal conditions, following ischemic injury, and during regeneration. We will focus on the racial background and sex as major risk factors for cardiovascular disease. Another important focus of the proposed studies is on the cell-secreted vesicles (exosomes) and their mRNA cargo, both as the readouts of cell state (e.g., during injury and regeneration) and as a cell-free therapeutic modality for ischemic heart. We hypothesize that the mature vascularized cardiac muscle generated from iPS cells from diverse patient populations (female vs male; African-American vs white) will be able to capture clinically observed differences in responses to cardiac ischemia, and that we will be able to specifically address these differences by sustained delivery of patient-tailored exosomes. To test this hypothesis, we propose three specific aims that will be pursued in an integrated fashion, with the outcomes of each aim informing the other two aims. Aim 1 is to engineer adult-like vascularized cardiac muscle from patient-specific iPSCs. Aim 2 is to develop an in vitro model of cardiac injury-regeneration using patient-specific iPSCs. Aim 3 is to establish mechanisms of exosome mediated signaling. We believe that this work will have impact on quantitative biological research and the development of bioengineering modalities for treating heart disease.